The invention relates to the technical field of lifting and handling appliances for boards made of wooden, composite, plaster or other materials designed to be placed on the ceilings and/or walls of a structure.
The Applicant has developed many appliances of this type which are marketed under the brand name LEVPANO and which are the subject of numerous patents.
These boards are large and are heavy loads to move and position; appliances of this type use telescopic masts which are raised manually by a winch. A broken-rope safety device is provided, this ensures that, if the traction rope used to raise or lower the sections that make up the mast fails, an additional safety rope takes over and acts as a substitute for the failed traction rope. A safety device of this type is described in French Patent No. 2538437 and has subsequently been improved by the device described in the Applicant's French Patent No. 2758150. The Applicant has used this patent to its satisfaction. FIG. 1 of the application shows the known safety device according to the prior art disclosed by French Patent No. 2758150. It employs a special arrangement of two ropes, a traction rope and a substitute safety rope, both these ropes being looped and separately attached by one of their ends to two shafts attached to the lower end of the terminal section of the mast having different positioning levels. The safety rope is therefore longer than the traction rope and is fitted in a manner that leaves slack between its lowest point and the retention shaft so that it is not used during normal operation. This safety rope is tensioned by a spring, one end of which is attached to the rope loop and the other end of which is attached to the inner section by means of a hole which allows fastening.
Although this device is widely used by the Applicant, it is not always practical to install it. The device is fitted inside the terminal section of the telescopic mast, as shown in FIG. 2 of above-mentioned French Patent No. 2758150.
The Applicant's approach was therefore to attempt to improve this safety device and the way it is fitted without compromising the necessary reliability and operating requirements.
The objective was therefore to externalise tensioning of the safety rope relative to the terminal section of the telescopic mast in order to make fitting the entire device easier.
The solution devised by the Applicant achieves this objective by completely rethinking the way in which the traction and safety ropes are attached compared with the previous practice described in the above-mentioned French patent.
This solution significantly improves the way in which the device is fitted by simplifying it and makes it possible, if applicable, for the maintenance operative to perform safety checks at any time without any particular difficulty by allowing immediate access to the device without the need to disassemble the telescopic mast assembly of the lifting appliance.
Thus, the safety device according to the invention meets the sought-after objective in terms of fitting, maintenance and cost, which are all drastically improved compared with the prior art.